Locating Columns with GPS

[bhiggins]

Hi All!

I have a large 15,000+ SF house project that we've designed. This house has roughly 50 embed plates for steel columns. The column placement is extra crucial to get correct, so the general contractor was asking us if there was a tool, software, or procedure to locate the columns using GPS. Ideally we would have some kind of 3D BIM model or drawing with column grid coordinates and they can use a tool to locate and stake the embed plate placement. The foundation is a stiffened slab on grade.

Anyone have any thoughts or ideas?

 

[KootK]

I don't think that even the military version of GPS is accurate enough to nail a column placement. They could probably hit you with a space laser but not use it to trim your nails.

 

[Ingenuity]

I would use laser/optical single-person setout tools like a HILTI PLT-300 optical layout tool for interior layouts Link; or the HILTI POS-18 robotic total station is more suited to exterior setouts. Link

Both are expensive systems, but you can upload DWG files to both and then in the field setout those points to an accuracy of 3mm, and vice-versa - take field points and download to DWG.

Very useful to layout interior walls and other set-outs too.

Tell your GC to get a demo from Hilti.

* Not employed by Hilti nor a distributor etc, - I just have a bunch of their tools and measurement system equipment.

 

[gte447f]

I'm not trying to be a smart***, but column layout is one of the most basic aspects of construction. If your GC is asking for help or shortcuts with this I would be very apprehensive.

 

[dhengr]

Bhiggins:
Why not just get the GC a 15000sf, steel A.B. template, so he doesn’t have to think or work too hard? You could teach a class in tape measure, chalk lines, and blue print reading, for contractor continuing ed. credits. I suppose this is one of those architectural wonders where no two things are on the same grid line, or in the same plane. You could also have the Arch. lay things out using his own plans and dimensions. That would be a fun thing to watch as it progressed over a several year period.

 

[TLHS]

Why are the exact locations unusually critical? Are the embed plates preattached to the columns or something? Normally you have reasonable fitup tolerance if you're embedding since you'll either have a grout pocket or a weld onto a plate depending on how you're approaching it.

 

[TLHS]

Have you taken a solid look at whether your requirements are reasonable? I don't know anything about the problem, but while this could be a contractor outside of their area of expertise, it could also be their response to try and cover their butt if they think you're asking for something unreasonable.

If it's the former, I'd avoid giving them anything more than general direction on means and methods because it makes it your problem if this routine task goes sideways. If it's the latter, see if you can fix the requirements rather than reinventing the wheel.

 

[CANPRO]

Agree with gte447f, this is routine for a steel contractor. The surveyor I work with would have that surveyed to within 1/8” and can export the data set into a 3D AutoCAD file.

Sounds like the carpenter getting into steel erection, which I’ve seen done with mixed results.

 

[BridgeSmith]

Differential GPS would be an option, if he's hung up on GPS, but as CANPRO indicated, any competent surveyor should be able to shoot/verify the column locations within an 1/8".

 

[Tmoose]

Will the house floor plan fit in an Envelope 125 foot square, or a 150 X 100 foot rectangle, or 300 X 50, or 500 X 500, or ??

 

[Tmoose]

"The column placement is extra crucial to get correct...."

Do you have a tolerance in mind and on the drawing for "correct" ?